Radiation Pneumonitis Risk after Bleomycin Toxicity in Hodgkin Lymphoma Patients

Introduction:

Combined modality treatment with Adriamycin, Bleomycin, Vinblastine and Dacarbazine (ABVD) chemotherapy followed by consolidative radiation to start within 3-4 weeks is the current accepted approach in the treatment of patients with early stage Hodgkin lymphoma (HL). Bleomycin pulmonary toxicity (BPT) is a well-known complication of treatment in HL patients. We undertook this study to investigate the risk of radiation pneumonitis (RP) in the setting of BPT and to determine the need for delay or omission of radiation in these patients.

Methods:

We reviewed the records of all HL patients treated with ABVD followed by radiation therapy (RT) to the chest between January 2009 and December 2014. We defined bleomycin toxicity as: the occurrence of clinical respiratory symptoms leading to discontinuation of bleomycin and/or bilateral opacities noted on computed tomography (CT) imaging and/or drop in diffusing capacity of the lung for carbon monoxide (DLCO) by 25%, in the absence of infection. We identified 129 patients, 100 of which received consolidation RT as part of combined modality and are the subject of this report, 29 patients were excluded because they developed relapse before getting RT. We compared patients with and without bleomycin toxicity for the following outcomes:

• Frequency of RP using the Pearson chi-square test.

• Interval between BPT and Radiation using Mann-Whitney U test (MWT)

• Interval between end of chemotherapy and radiation using MWT.

We used univariate Cox regression analysis to assess the risk of RP by looking at the time-interval in weeks from end of bleomycin to start of RT.

Results:

Median follow up was 23 months (6 - 69), Median age was 31 years (18-77), and 60% were females. Per our criteria, 28 patients developed BPT (25.5%). All patients received intensity modulated radiation therapy, radiation dose median was 30.60 Gy (20-42Gy). Mean lung dose (MLD) was a median of 9.4 Gy (2.6- 13.9 Gy). The median interval between chemotherapy and RT was 3 weeks (1- 8 weeks). Median interval from stopping bleomycin, either as a precaution or because of toxicity, to the start of RT was 5 weeks (1-20 weeks). Interval between documented bleomycin toxicity to start of radiation was a median of 8.5 weeks (2-20 weeks).

We had 10 cases of RP (10%), 5 of which were ≥ Grade 2. There was no significant difference in RP risk in patients with or without BPT; 10.7% (3/28) versus 9.6% (7/72) respectively, P= 0.82.

Patients with BPT versus those without BPT had no significant difference in baseline characteristics. The interval time from chemotherapy to radiation was a median of 3 weeks in both groups with or without BPT showing no difference; P= 0.83. However, Patients with BPT had a significantly longer interval from last bleomycin cycle to start of radiation compared to those without BPT (median 8.5 vs. 5 weeks, p =0.014).

The intervals from chemotherapy to radiation treatment and from bleomycin to radiation treatment showed no significant correlation with RP on univariate Cox regression analysis (P= 0.41 and P= 0.12, respectively). This was maintained when adjusted for the number of bleomycin cycles.

Treatment of BPT

Of the 28 patients, 17 were managed by stopping bleomycin and observation only; 10 patients required a 2 week course of steroids. One patient went into severe respiratory compromise, was started on continuous oxygen and eventually recovered 48 hours later and went on to receive RT beginning 2 weeks after completing his steroid treatment. This patient did not have pulmonary complications after RT.

All 28 BPT patients eventually completed their planned course of radiation. At last follow up, all 28 patients were alive and free of respiratory symptoms.

Conclusion:

In our cohort of Hodgkin lymphoma patients, those patients with bleomycin toxicity who received standard RT had no excess risk of subsequent RP. Moreover, patients were able to receive complete courses of RT to intended conventional radiation doses. Our findings suggest that RT does not need to be delayed following chemotherapy, except to allow for the completion of steroids or clinical recovery from BPT.